Floor panel with edge connectors

ABSTRACT

Floor covering, including hard floor panels ( 1 ) which, at least at the edges of two opposite sides ( 2-3, 26-27 ), are provided with coupling parts ( 4-5, 28-29 ), cooperating which each other, substantially in the form of a tongue ( 9-31 ) and a groove ( 10-32 ), wherein the coupling parts ( 4-5, 28-29 ) are provided with integrated mechanical locking elements ( 6 ) which prevent the drifting apart of two coupled floor panels in a direction (R) perpendicular to the related edges ( 2-3, 26-27 ) and parallel to the underside ( 7 ) of the coupled floor panels ( 1 ).

RELATED APPLICATION DATA

This application is a continuation of application Ser. No. 08/872,044filed Jun. 10, 1997 now U.S. Pat. No. 6,006,486.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a floor covering, made of hard floor panels.

2. Related Technology

In the first instance, the invention is intended for so-called laminatedfloors, but generally it can also be applied for other kinds of floorcovering, consisting of hard floor panels, such as veneer parquet,prefabricated parquet, or other floor panels which can be compared tolaminated flooring.

It is known that such floor panels can be applied in various ways.

According to a first possibility, the floor panels are attached at theunderlying floor, either by glueing or by nailing them on. Thistechnique has a disadvantage that is rather complicated and thatsubsequent changes can only be made by breaking out the floor panels.

According to a second possibility, the floor panels are installedloosely onto the subflooring, whereby the floor panels mutually matchinto each other by means of a tongue and groove coupling, whereby mostlythey are glued together in the tongue and groove, too. The floorobtained in this manner, also called a floating parquet flooring, has asan advantage that it is easy to install and that the complete floorsurface can move which often is convenient in order to receive possibleexpansion and shrinkage phenomena.

A disadvantage with a floor covering of the above-mentioned type, aboveall, if the floor panels are installed loosely onto the subflooring,consists in that during the expansion of the floor and its subsequentshrinkage, the floor panels themselves can drift apart, as a result ofwhich undesired gaps can be formed, for example, if the glue connectionbreaks.

In order to remedy this disadvantage, techniques have already beenthrough of whereby connection elements made of metal are providedbetween the single floor panels in order to keep them together. Suchconnection elements, however, are rather expensive to make and,furthermore, their provision or the installation thereof is atime-consuming occupation.

Examples of embodiments which apply such metal connection elements aredescribed, among others, in the documents WO 94/26999 and WO 93/13280.

Furthermore, couplings are known which allow coupling parts to snap fitinto each other, e.g., from the documents WO 94/1628, WO 96/27719 and WO96/27721. The snapping-together effect obtained with these forms ofembodiment, however, does not guarantee a 100-percent optimumcounteraction against the development of gaps between the floor panels,more particularly, because in fact well-defined plays have to beprovided in order to be sure that the snapping-together is possible.

From GB 424.057, a coupling for parquetry parts is known which, inconsideration of the nature of the coupling, only is appropriate formassive wooden parquetry.

Furthermore, there are also couplings for panels known from thedocuments GB 2.117.813, GB 2,256.023 and DE 3.544.845. These couplings,however, are not appropriate for connecting floor panels.

BRIEF SUMMARY OF THE INVENTION

The invention aims at an improved floor covering of the aforementionedtype, the floor panels of which can be coupled to each other in anoptimum manner and/or the floor panels of which can be manufactured in asmooth manner, and whereby preferably one or more of the aforementioneddisadvantages are excluded.

The invention also aims at a floor covering which has the advantage thatno mistakes during installing, such as gaps and such, can be created.

Furthermore, the invention also aims at a floor covering whereby thesubsequent development of gaps is excluded or at least counteracted inan optimum manner, whereby also the possibility of the penetration ofdirt and humidity is minimalized.

To this aim, the invention relates to a floor covering, consisting ofhard floor panels which, at least at the edges of the two oppositesides, are provided with coupling parts, cooperating which each other,substantially in the form of a tongue and a groove, wherein the couplingparts are provided with integrated mechanical locking elements whichprevent the drifting apart of two coupled floor panels into a directionperpendicular to the related edges and parallel to the underside of thecoupled floor panels. Hereby, these coupling parts are optimalized insuch a manner that they allow that any form of play is counteracted andpreferably is excluded.

By integrated mechanical locking elements is understood that these forma fixed part of the floor panels, either by being connected in a fixedmanner to the floor panels, or by being formed in one piece therewith.

In a first important preferred form of embodiment, the coupling partsare provided with locking elements which, in the engaged position of twoor more ofsuch floor panels, exert a tension force upon each other whichforce the floor panels towards each other. As a result of this that notonly the formation of gaps counteracted during installation, but also ina later stage the development of gaps, from any causes whatsoever, iscounteracted.

According to another characteristic of the intention, the couplingparts, hereby are formed in one piece with the core of the floor panels.

According to a second important preferred embodiment, the aforementionedoptimalization is achieved in that the floor covering panel possessesthe following combination of characteristics: the coupling parts andlocking elements are formed in one piece with the core of the floorpanels; the coupling parts have such a shape that two subsequent floorpanels can be engaged into each other exclusively by snapping togetherand/or turning, whereby each subsequent floor panel can be insertedlaterally into the previous; the coupling parts are interlocked freefrom pay in all directions in a plane extending perpendicular to theaforementioned edges; the possible difference between the upper andlower lip of the lips which border the aforementioned grooves, measuredin the plane of the floor panel and perpendicular to the longitudinaldirection of the groove, is smaller than one time the total of thethickness of the panel; the total thickness of each related floor panelis larger than or equal to 5 mm; and that the basic material of thefloor panels, of which the aforementioned core and locking elements areformed, consists of a ground product which, by means of a binding agentor by means of melting together, is made into a unitary composite,and/or of a product on the basis of synthetic material and/or of a chipboard with fine chips.

Due to the fact that the coupling parts provide for an interlocking freefrom play, as well as due to the fact that these coupling parts aremanufactured in one piece, from the basic material of the floor panels,a perfect connection between adjacent floor panels can always beguaranteed, even with repeated expansion and shrinkage of the floorsurface.

This combination of characteristics can be combined or not with theaforementioned characteristic that the locking elements exert a tensionforce upon each other when panels are joined together.

According to a third important preferred embodiment, the characteristicsof which may or may not be combined with the characteristics of theembodiments described above, the floor covering is characterized in thatthe lower lip which limits or defines the lower side of the groove,extends beyond the upper lip in the plane of the panel; the lockingelements are formed at least of a contact portion which inwardly slopesdownward; and that this portion, at least partially, is located in theportion of the lower lip which extends beyond the upper lip. Theadvantages of these features will appear from the further description.

According to a preferred form of embodiment, the floor panels areconfigured as elongated panels and the coupling parts described aboveare applied along the longitudinal sides of these panels.

According to a particular form of embodiment, coupling parts areprovided at the other two sides, too, either of another constructionthan described above or not.

In the most preferred form of embodiment, for the basic material useshall be made of the aforementioned product, which, as said, is groundand, by means of a binding agent, made into a unitary compositematerial. More particularly, for the core use shall be made offinely-ground wood which preferably is glued, more particularly,moisture resistant glued. Still more particularly, for the core useshall be made of so-called HDF board (High Density Fibreboard) or MDFboard (Medium Density Fibreboard) which is highly compressed ground woodparticles and binder material. Hereinafter, the wood component of thecore material shall be referred to as “wood product”.

The fact that the invention is applied to floor panels the basicmaterial of which consists of the material described above, offers theadvantage that with he processing of this material, very smooth surfacesare obtained whereby very precise couplings can be realized, which, infirst instance, is important in the case of a snap-together connectionand/or turning connection free from play. Also, very special forms ofcoupling parts can be manufactured in a very simple manner because theaforementioned kinds of material can be processed particularly easy.

The surfaces obtained with HDF and MDF also have the advantage that thefloor panels mutually can be shifted readily alongside each other ininterlocked condition, even when engaged with a tensioning force.

The applicants also discovered that the aforementioned materials, inparticular HDF and MDF, show ideal features in order to realize aconnection, such as mentioned above, as these material show the rightfeatures in respect to elastic deformation in order to, on the one hand,realize a snap-together effect, and, on the other hand, receiveexpansion and shrinkage forces in an elastic manner, whereby it isavoided that the floor panels come unlocked or are damaged in anirreparable manner.

In the case that for the core use is made of a material based onsynthetic material, to this end solid synthetic material can be used aswell as a mixture of synthetic materials, eventually composed ofrecycled materials.

The floor covering preferably is formed by joining the floor panels intoeach other free of glue. Hereby, the connections are of such nature thatthe floor panels can be disassembled without being damaged, such that,for example, when moving from one residence or location to another, theycan be taken along in order to be placed down again. It is, however,clear that a glueing between tongue and groove is not excluded.

The invention, of course, also relates to floor panels which allow therealization of the aforementioned floor covering.

The invention also relates to a method for the manufacturing of theaforementioned floor panels with which the advantage that the tonguesand/or grooves, including the corresponding locking means, can beprovided at the floor panels at high production speeds without problems.More particularly, it aims at a method which allows that the rathercomplicated forms of the tongue and the groove of the aforementionedfloor panels can be formed completely by means of milling cutters, thediameter of which can be chosen independent of the form to be realized,such that the use of small milling cutters, for example finger cutters,with diameters smaller than the depth of the tongue or groove can beexcluded.

In accordance with this method the tongue and/or groove is formed bymeans of a milling process using at least two sequential milling cyclesor passes by means of milling cutters which are positioned at differentangles in respect to the related floor panel. During each of theaforementioned milling cycles, preferably substantially the final formof one flank, either of the tongue or of the groove, is formed.

For the aforementioned two milling cycles, thus, milling cutters areused which extend outside the groove, respectively the tongue. Moreparticularly the diameters of these milling cutters shall at least be 5times and even better 20 times larger than the thickness of the floorpanels.

The use of milling cutters having the aforementioned diameters has as anadvantage that the normal production speeds can be maintained which arealso applied during milling of a classical straight tongue and groove.There is also the advantage obtained that the installation of suchmilling cutters induce only minor or no additional costs because suchmilling cutters can be placed directly upon a motor shaft and/or theconventional machines can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

With the intention of better showing the characteristics according tothe invention, in the following, as an example without any limitativecharacter, several preferred forms of embodiment are described, withreference to the accompanying drawings, wherein:

FIG. 1 represents a floor panel of a floor covering according to theinvention;

FIG. 2, on a larger scale, represents a cross-section according to lineII—II in FIG. 1;

FIGS. 3 and 4 represent how two floor panels with coupling partsaccording to FIG. 2 match into each other;

FIG. 5, on a larger scale, represents a cross-section according to lineV—V in FIG. 1;

FIGS. 6 and 7 represent how two floor panels with coupling partsaccording to FIG. 5 match into each other;

FIGS. 8 to 11 represent a number of variants of coupling parts of floorpanels according to the invention;

FIG. 12 schematically represents how the floor parts can be providedwith coupling parts;

FIG. 13 represents a cross-section according to line XIII—XIII in FIG.12;

FIGS. 14 to 21, on a larger scale and in cross-section, represent thepenetration of the milling cutters which are indicated in FIG. 12 witharrows F14 to F21;

FIG. 22 represents a floor panel according to the invention;

FIG. 23, on a larger scale, represents the coupling of two floor panelsof FIG. 22;

FIGS. 24 and 25 represent two manners of coupling floor panels accordingto FIG. 22 to each other.

DETAILED DESCRIPTION

The invention relates to a floor covering which is composed of hardfloor panels 1, for example, such as a laminated panel as shown in FIG.1.

These floor panels 1 can be of various shape, for example, rectangularor square, or of any other shape.

In the most preferred form of embodiment, they shall be manufactured inan elongated form, such as shown in FIG. 1, for example, with a lengthof 1 to 2 meters. The thickness, however, can also vary, but ispreferably 0.5 to 1.5 cm, and more particularly 0.8 cm.

Each floor panel 1 is, at least at the edges of two opposite sides 2-3,provided with coupling parts 4-5 which permit two adjacent identicalfloor panels 1 to be coupled to each other.

According to the invention, the coupling parts 4-5, as represented inthe FIGS. 2 to 4, are provided with integrated mechanical locking partsor locking elements 6 which prevent the drifting or sliding apart of twocoupled floor panels 1 in a direction D perpendicular to the respectivesides 2-3 and parallel to the underside 7 of the coupled floor panels 1;the coupling parts 4-5 and the locking elements 6 are formed in onepiece with the core 8 of the floor panels 1; the coupling parts 4-5 havesuch a shape that two subsequent floor panels 1 can be engaged into eachother solely by snapping-together and/or turning after the couplingparts are partially engaged, whereby each subsequent floor panel 1 canbe laterally inserted into the previous; and the coupling parts 4-5preferably are interlocked free from play in all directions in a planewhich is located perpendicular to the aforementioned edges.

In the case of floor panels 1 with an elongated shape, as represented inFIG. 1, the respective coupling parts 4-5 are located at thelongitudinal sides 2-3.

The coupling parts 4-5 can be realized in various forms, although thebasic forms thereof will always be formed by a tongue 9 and a groove 10.

In the form of embodiment of FIGS. 2 to 4, the related floor panel 1 isprovided with coupling parts 4-5 and locking means or locking elements 6which allow two floor panels 1 to be mutually engaged by means of aturning movement, without the occurrence of any snap-together effect.

In the represented example, the locking elements 6 consist of a firstlocking element 11, formed by a protrusion with a bent round shape atthe lower side 12 of the tongue 9, and a second locking element 13(shown in FIG. 2), formed by a recess with a bent hollow or downwardlyconcave shape in the lower wall 14 of the groove 10.

The locking elements 11-13 ensure that two floor panels 1 which arecoupled to each other can not move laterally in the horizontal planewith respect to each other.

In order to enable two floor panels 1 to be inserted into each other bymeans of a turning movement, the curvatures preferably are circular. Thebottom side 12 of locking means or locking elements 6 has a curvaturewith a radius R1, the center of which coincides with the respectiveupper edge 15 of the floor panel 1, whereas the lower wall 14 of thelocking part 5 has a curvature with a radius R2 which is equal to theradius R1, but its center coincides with the respective upper edge 16.Radii R1 and R2 may also be applied which are larger or smaller than thedistance to the upper edge 15, 16 respectively, and/or which differ fromeach other in size.

The upper side 17 of the tongue 9 and the upper wall or side 18 of thegroove 10 are preferably flat and preferably are located in thehorizontal plane.

The inner side 20 of the groove 10 and the 4 front side 19 of the tongue9 of the two interlocked floor panels 1 preferably do not fit closelyagainst each other, such that an intermediate space 21 is createdbetween them into which possible dust remainders or such can be pushedaway by means of the tongue 9.

The tongue 9 and the groove 10 preferably have shapes which arecomplementary to each other, such that the tongue 9 in the engagedcondition of two identical floor panels 1 precisely sits against theupper wall 18 and the lower wall 14 of the groove 10, whereby a pressureP, exerted against the upper lip 22, is received or reacted not only bythis lip 22, but by the complete structure, because this pressure can betransmitted through the tongue 9 and the lower lip 23 to cause thepanels to be urged towards each other.

It is, however, clear that a number of minor deviations to thesecomplementary forms can occur which, anyhow, have no or almost no effectupon the receipt and transmission of pressure forces. For example, achamfer 24 and lip 22 on a recess 25 can be provided, as represented inFIGS. 2 to 4, as a result of which the subsequent floor panels 1 caneasily be pushed and guided into each other, such that no possibleridges in the subflooring or such render good insertion difficult.

As represented in the FIGS. 5 to 7, the floor panels 1 according to theinvention can also, along the sides 26-27 which are at a right angle tothe sides 2-3, be provided with coupling parts 28-29 which have lockingelements 30, too. The coupling parts 28-29 are preferably also realizedin the shape of a tongue 31 and a groove 32. Hereby, the lockingelements 30 do not have to be of the same nature as the locking elements6.

Preferably, at the sides 26-27 locking elements are provided which allowfor an engagement and interlocking by means of a lateral translationmovement in direction T only, as represented in FIGS. 6 and 7. To thisaim, the locking elements 30 consist of a snap-together connection withlocking elements 33 and 34 which grip behind each other.

As represented in FIGS. 5 to 7, the locking element 33 preferablyconsists of a protrusion of the lower side 35 of the tongue 31 which canbe located in a recess 36 in a lower lip 43 extending distally from thelower wall 37 of the groove 32. The locking element 34 is formed by theupward directed part or protrusion which defines the distally outer endof recess 36.

In this case, the locking elements 33-34 have contact surfaces 38-39which are parallel to each other and preferably extend in an inclinedmanner, according to a direction which simplifies the snapping-togetherof the panels. The common plane of tangency L which is determined by thecommon tangent at the meeting point or area of surfaces 38-39, herebyforms an angle A sloping inwardly and downwardly from an outer region toan inner region relative to the underside 7, which angle is smaller than90°.

The locking elements 33-34 preferably are provided with inclinedportions 40 and 41 which, when two floor panels 1 are engaged, cooperatewith each other in such a manner that the locking elements 33-34 caneasily be pushed over each other until they grip behind each other bymeans of a snap-together effect (FIGS. 6 and 7).

The thickness W1 of the tongue 31 preferably is equal to the width W2 ofthe groove 32, such that compression pressure P applied to the upper lip42 is reacted by the tongue 31 which, in its turn, then is reacted bythe lower lip 43.

Analogous to the chamfer 24 and recess 25, a recess 44 and a chamfer 45are provided also at the edges 28-29.

It is noted that such a snap-together coupling can also be applied atthe edges 2-3. Hereby, this can be a snap-together coupling analogous tothese of FIGS. 5 to 7, but this can also be a snap-together couplingusing other forms of coupling configurations, for example, such asrepresented in FIGS. 8 and 9. Contrary to the locking elements 33-34which consist of rather local protrusions, in the forms of embodiment ofFIGS. 8 and 9 use is made of locking elements 46-47 which, in comparisonto the total width B of the coupling, extend over a rather largedistance.

In this case, the locking elements 46-47 are also provided at the lowerside 12 of the tongue 9 and the lower wall 14 of the groove 10.

According to FIG. 8, the locking elements 46-47 have contact surfaces48-49 which are at an angle with the plane of the floor panel 1. In thismanner, a coupling is obtained which is interlocked in a particularlyfixed manner.

As represented in FIG. 9, the locking elements 46-47 possibly can beconfigured in such a manner that substantially only a linear contact isobtained, for example, because the contact surfaces directed towardseach other are formed with different curvatures.

The surfaces, directed towards each other, of the locking elements 46-47hereby consist of curved surfaces. The common plane of tangency L formsan angle A which is smaller than 90°, and more preferably is smallerthan 70°.

In this manner, the locking element 46 preferably has two portions witha different curvature, on one hand, a portion 50 with a strong curvatureand, on the other hand, a portion 51 with a weak curvature. The portion50 with the strong curvature provides for the formation of a firmcoupling. The portion 51 with the weak curvature facilitates thecoupling parts 4-5 to be brought into each other easily. Theintermediate space S forms a chamber which offers space for dust and thelike which, when engaging two floor panes 1, inevitably infiltratesthere.

In the case of a snap-together connection, for example, a connectionsuch as represented in FIGS. 7 to 9, preferably the tongue 9-31 has ashape that thickens from below, which then can cooperate with a widenedportion in the groove 10.

In FIG. 10, a variant is represented whereby at least at the level ofthe upper edges 15-16, a sealing material 52 is provided, as a result ofwhich a watertight sealing can be assured. This sealing material 52 mayconsist of a strip or covering which is provided previously at the floorpanel 1, either at one or both upperside edges 15-16.

In FIG. 11, a further variant is represented, whereby the lockingelement 6 is formed by an upward directed portion 53 at the tongue 9,which as a result of a turning movement of the panel, is brought behinda downward-directed portion 54 on the upper wall 18. More particularly,this is obtained by forming the upper side 17 and the upper wall 18 witha curvature R3, the center of which is situated at the upperside edges15-16, and forming the lower side 12 and the lower wall 14 with a radiusR4, the center of which is also situated at the upperside edges 15 and16, respectively. These radii R3-R4 can be chosen otherwise, too.

In general, according to the invention, the difference between, on onehand, the radius R1, R3 respectively, and, on the other hand, the radiusR2, R4 respectively, preferably should not be larger than 2 mm.

It is also preferred that the center of these radii be situated insidethe circle C1, C2 (see FIG. 2) respectively, which extends with a radiusR5 of 3 mm centered at upperside edge 15, 16 respectively.

Finally is noted that, according to the invention, the lower lip 23-43,as represented in FIGS. 2 to 7, can be formed distally longer than theupper lip 22-42. This has an advantage that the coupling parts 4-5-28-29can be shaped in an easier manner by means of a milling cutter or thelike. Furthermore, this simplifies the engagement of two floor panels 1,because each subsequent floor panel 1 during installation can be placedupon the protruding lower lip 23-43, as a result of which the tongue9-31 and the groove 10-32 automatically are positioned in front of eachother.

The embodiments wherein the lower lip 23 is equal to or distally shorterthan the upper lip 22, in their turn, offer the advantage that noprotruding lip 23 remains at the extreme edge of the floor which mightcause problems in finishing the floor installation.

In order to allow for a smooth assembly, to guarantee the necessarystability and firmness and in order to limit the quantity of material tobe cut away, the difference E between the distally outer edge of theupper lip 22-42 and the distally outer edge of the lower lip 23-43,measured in the plane of the floor panel and perpendicular to thelongitudinal direction of the groove 10, should preferably be keptsmaller than one time the total thickness F of the floor panel 1. Forstability's sake, normally this total thickness F shall never be lessthan 5 mm.

The small dimension of the difference E offers the advantage that thelower lip need not be strengthened by a reinforcement strip or the like.

According to a particular form of embodiment, the central line M1through the tongue 9 and the groove 10 is situated lower than the centerline M2 of the floor panel 1, such, that the upper lip 22-42 is thickerthan the lower lip 23-43. In first instance, this is essential in thiskind of connection, because then it is the lower lip 23-43 which bends,whereby the upper side of the floor panel 1 is kept free of possibledeformations.

As explained in the introduction, for the core 8 a material is chosenfrom the following series:

a. a ground product which, by means of a binding agent or by means ofmelting together is made into a unitary composite material;

a product based on synthetic material;

chip board with fine chips.

The invention shows its usefulness, in first instance, preferably withlaminated flooring, due to the reasons explained in the introduction.

As represented in the examples of the FIGS. 2 to 11, such laminatedflooring preferably consists of a core 8 made of MDF medium densityfiberboard board, HDF high density fiberboard board or similar, wherebyat least at the upper side of this core 8 one or more layers of materialare provided.

More particularly, it is preferred that the laminated flooring isprovided with a decorative layer 55 and a protective top layer 56. Thedecorative layer 55 is a layer, impregnated with resin, for example,made of paper, which can be imprinted with a variety of patterns, suchas a wood pattern, a pattern in the form of stone, cork, or similar oreven with a fancy pattern. The protective top layer 56 preferably alsoconsists of a layer saturated with resin, for example, melamine resin,which in the final product is transparent.

It is clear that still other layers can be applied, such as anintermediate layer 57 upon which the decorative layer 55 is provided.

Preferably, also a backing layer 58 shall be applied at the underside 7,forming a counterbalancing element for the top layers and, thus,guaranteeing the stability of the form of the floor panel 1. Thisbacking layer 58 may consist of a material, for example paper,impregnated with a resin, for example, a melamine resin.

As represented schematically in FIG. 12, the tongue 9 and the groove 10,and preferably also the tongue 31 and the groove 32 are formed by meansof a milling process. In the case that a profile has to be applied onall four sides, the floor panels 1 preferably shall be displaced bymeans of two sequential perpendicular movements V1 and V2, wherebyduring the first movement profiles at two opposite edges are provided,in this case the longitudinal edges, by means of milling devices 59-60,whereas during the second movement profiles are provided at the otheredges, in this case the small edges, by means of milling devices 61-62.During these processing, the floor panels 1 preferably are put withtheir decorative layer directed downward.

According to an important characteristic of the invention, eachrespective tongue 9-31 and groove 10-32 are formed by means of a millingprocess with at least two sequential milling cycles or passes by meansof milling cutters which are positioned at different angles in referenceto the related floor panel 1.

This is illustrated in FIGS. 13, 14 and 15, wherein it is representedhow a groove 10 is realized by means of two milling cycles by means oftwo milling cutters 63 and 64. FIGS. 16 and 17 represent how the tongue9 is shaped by means of milling cutters 65 and 66.

The FIGS. 18-19 and 20-21 represent similar views showing how the groove32 and the tongue 31 are shaped by means of milling cutters 67-68 and69-70, positioned at an angle.

During each of the aforementioned milling passes, substantially thefinal shape of one flank is fully realized. For example, the millingcutter 63 of FIG. 14 determines the final shape of the lower flank 71 ofthe groove 10, whereas the milling cutter 64 determines the final shapeof the upper flank 72.

As mentioned in the introduction, preferably milling cutters 63 to 72shall be used, having diameters G which are at least 5 times, and evenbetter at least 20 times larger than the thickness F of the floor panels1.

Apart of the mentioned milling cutters, preferably still other millingcutters are applied, for example, in order to remove a part of thematerial to be removed during a first premachining cycle.

In the FIGS. 22 to 25, a particularly preferred form of embodiment of afloor panel 1 according to the invention is represented. Hereby, theparts which correspond with the previous embodiments are indicated withcorresponding references.

An important characteristic herein consists in that the coupling parts4-5 are provided with locking elements 6 which, in engaged conditionwith the panels in a common plane, exert a tension force upon eachother, as a result of which the engaged floor panels 1 are forcedtowards each other in compression. As represented, this is realizedpreferably by providing the coupling parts with an elastically yieldableor bendable portion, in this case the lower lip 43, which, in engagedcondition, is at least partially bent and in this way creates a tensionforce which results in the engaged floor panels 1 being forced towardseach other. The resultant bending V, as well as the tension force K, areindicated in the enlargement view of FIG. 23.

In order to obtain the tension force K pressing together the engagedfloor panels 1, the bendable portion, in this case the lip 43,preferably is provided, as represented, with an inwardly and downwardlyinclined contact surface 73 which preferably can cooperate with acorresponding contact surface 74 on tongue 9. These contact surfaces73-74 are similar to the aforementioned contact surfaces 39-38 and alsosimilar to the inclined portions of the lower lip of FIGS. 2 to 4.

In the FIGS. 2 and 5, the portions form complementary matching shapes;it is, however, clear that, by a modification, also a tension effectsimilar to that shown in FIG. 23 can be realized.

Due to, on one hand, the contact along the angle A, and, on the otherhand, the fact that a tension force K is created, a compression forcecomponent K1 is produced, as a result of which the floor panels 1 aredrawn against each other in compression.

Preferably, the angle A of the mutual plane of tangency of contactsurfaces 73-74 relative to the horizontal plane is situated between 30and 70 degrees. In the case that use is made of the embodiment whereby atension force K is realized, an angle A of 30 to 70 degrees is ideal inorder, on one hand, to effect an optimum pressing-together of the floorpanels 1 and, on the other hand, to ensure that the floor panels 1 caneasily be engaged and respectively disassembled.

Although the pressing or compression force component K1 preferably isdelivered by the aforementioned lip 43, the invention does not excludeother forms of locking elements or structures whereby this force isdelivered by other bendable portions.

It is noted that the bending V is relatively small, for example, severalhundredths up to several tenths of a millimeter, and does not have aninfluence upon the placement of the floor covering. Furthermore itshould be noted that such floor covering generally is placed upon anunderlayer (not shown) which is elastically compressible, as a result ofwhich the bending V of the lip 43 only produces local bending of theunderlayer.

Due to the fact that the lip 43 is bent apart and that it remainssomewhat bent apart in engaged position, the additional advantage isobtained that, when exerting a pressure upon the floor covering, forexample, when placing an object thereupon, the pressing-togethercompressive force is enhanced and, thus, the development of gaps iscounteracted even more.

It is noted that the inventors have found that, contrary to allexpectations, an ideal tension force can be realized by manufacturingthe coupling parts 4-5, including the locking elements 33-34, andpreferably the complete core 8, of HDF board or MDF board, althoughthese material normally only allow a minor elastic deformation.

HDF and MDF also offer the advantage that smooth surfaces are obtained,as a result of which the locking elements can be moved easily over eachother.

According to a variant of the invention, the tension force can also besupplied by means of an elastic compression of the material of thecoupling parts themselves, to which end these coupling parts, andpreferably the complete core 8, would be manufactured using anelastically compressible material.

A further particular characteristic of the embodiment of FIGS. 22 to 25consists in that the floor panels 1 can be selectively engaged by meansof a turning movement, as represented in FIG. 24, as well as by means oflaterally shifting them towards each other in substantially a commonplane, as represented in FIG. 25, preferably in such a manner that,during the engagement by means of the turning movement with the couplingparts partially engaged, a maximum bending Vm results in the couplingparts, more particularly in the lip 43, which bending Vm is lesspronounced, if not nonexistent, as in the FIGS. 2 to 4, in comparison tothe bending Vm which results when the floor panels 1 are engaged bymeans of shifting them towards each other, as in FIG. 15.

The advantage of this consists in that the floor panels 1 can be engagedeasily by means of a turning movement, without necessitating use of atool therefore, whereas it still remains possible to engage the floorpanels also by means of shifting them laterally. This latter is useful,in first instance, when the last panel has to be placed partially undera door frame or similar situation. In this case, the floor panel 1 canbe pushed under the door frame with the side which does not have to beengaged and subsequently, possibly by means of tools, can be snappedinto the adjacent floor panel by lateral sliding together.

It is noted that the shapes of the coupling parts 4-5 shown in FIGS. 22to 25 can also be used for the coupling parts 28-29 of the short sidesof the panels.

According to the invention, in the case that the four sides 2-3-26-27are provided with coupling pars 4-5-28-29, these coupling parts can beformed in such a manner that in one direction a firmer engagement thanin the other direction is effected. In the case of elongated floorpanels 1, for example, such as represented in FIG. 1, the locking at thesmall sides 26-27 preferably shall be more pronounced than at thelongitudinal sides 2-3. The length of the parts at the small sides,namely, is smaller and, in principle, less firm. This is compensated forby providing a more pronounced locking.

This difference in engagement can be obtained by shaping the contactsurfaces 73-74 with different angles.

Preferably, the aforementioned protrusion, more particularly the lockingelement 33, is bounded by at least two portions 75-76 (shown in FIG.22), respectively a portion 75 with a strong (steep) inclination whichprovides for the locking, and a portion 76 with a weaker (less inclined)inclination which renders the engagement or guidance of the couplingparts easier. In the embodiment of FIGS. 22 to 25, these portions 75-76are formed by straight planes, but, as already described with referenceto FIG. 9, use can also be made of curved portions 50-51. In FIG. 5,these are the contact surface 38 and the inclined portion 40.

In the preferred form of the invention, the floor panels 1 comprisecoupling parts 4-5 and/or 28-29 exhibiting one of the following or thecombination of two or more of the following features:

a curvature 77 (shown in FIG. 22) at the lower side of the tongue 9and/or a curvature 78 at the lower lip 43 which form a guidance whenturning two floor panels 1 into each other, with the advantage that thefloor panels 1 can be engaged into each other easily duringinstallation;

roundings 79-80 at the edges of the locking elements 33-34, with theadvantages that the locking elements can easily shift over each otherduring their engagement, or during disassembly of the floor panels 1 andthat the locking elements will not be damaged, for example, crumble awayat their edges, even if the floor panels are engaged and disassembled;

dust chambers 81, or spaces 21 as in FIG. 4, between all sides, directedlaterally towards each other, of the engaged floor panels 1, with theadvantage that inclusions which get between the floor panels 1 duringthe engagement do not exert an adverse influence upon good engagement;

a shaping of the tongue 9 which is such, for example, by the presence ofa chamfer 82, that the upper side of the tongue 9 becomes situated fromthe first joining together or substantial contact of the panels, underthe lower side of the upper lip 42 when the floor panels 1 are pushedtowards each other in substantially the same plane, as indicated in FIG.25, with the advantage that the front extremity or end of the tongue 9does not press against the front side of the upper lip 42 or the frontedge of the bottom lip 43 when the floor panels are pushed towards eachother in the same plane;

a ramp surface 83, hereinbefore also called inclined portion 41, formedat the distally outer end of the lower lip 43, with the advantage thatthe locking elements 33-34 shift smoothly over each other and that thelower lip 43 is bent uniformly;

in the engagement direction only one important contact point which isformed by a section 84 at the location of the upperside edges of thefloor panels 1, with the advantage that the aforementioned tension forceis optimally transferred to the upper side of the floor panels 1 andthat the development of openings between the floor panels 1 iscounteracted;

contact surfaces 85-86, more particularly abutment surfaces, formed bythe upper side of the tongue 9 and the upper side of the groove 10which, over the largest portion of their length, are flat and runparallel to the plane which is defined by the floor panels 1, as well ascontact surfaces cooperating with each other, formed by curvatures77-78, with the advantage that no mutual displacement in height betweentwo engaged floor panels 1 is possible, even if the insertion depth ofthe tongue 9 into the groove 10 should vary due to various causes; inother words, no height differences may occur between the adjacent floorpanels.

In the embodiment of FIGS. 22 to 25, all these characteristics arecombined; it is, however, clear that, as becomes evident from FIGS. 2 to11, these features can also be provided separately or in a limitedcombination with one another.

As becomes evident from FIGS. 5 to 7 and 22 to 25, an importantcharacteristic of the preferred embodiment of the invention consists inthat the cooperative locking element 6, in other words, the portionproviding for the snap-together and engagement effect, are situated inthat portion of the lower lip 23-43 which extends beyond the distal edgeof the upper lip 22-42, more particularly, the lowermost point 87 of thelocking part 33 is situated under the top layer of the floor panel 1.For clarity's sake, this top layer is indicated in the FIGS. 22-25 onlyas a single layer.

It should be noted that the combination of features, the lower lip 23-43extending further than the upper lip 22-42; the locking elements 6 beingformed at least by means of a contact surface portion which inwardlyslopes downward, and wherein this portion, at least partially, islocated in the portion of the lower lip 23-43 which extends distallybeyond the upper lip 22-42, is particularly advantageous, among others,in comparison with the couplings for floor panels described in thedocuments WO 94/01628, WO 94/26999, WO 96/27719 and WO 96/27721. Thesloping contact surface portion offers the advantage that the floorpanels 1 can be disassembled again. The fact that this sloping portionis situated in the extended portion of the lower lip 23-43 adds theadvantage that no deformations can occur during coupling which manifestthemselves up to the top layer.

According to a preferred characteristic of the invention, theaforementioned portion, i.e. the contact surface 39 or 73, preferablyextends in such a manner that the distance between the upper edge 16 ofthe panel to the contact surface 39, 73 diminishes between the proximaland distal ends of the sloping contact surface 39, 73, in other words,such that, as represented in FIG. 22, the distance X2 is smaller thanthe distance X1. This is also the case in FIG. 7.

Still preferably, this portion only starts at a clear distance E1 fromthe outer edge of upper lip 42.

It is obvious that the coupling parts 22 to 25 can also be shaped bymeans of said milling process.

According to a particular characteristic of the invention, the floorpanels 1 are treated at their sides 2-3 and/or 26-27 with a surfacedensifying agent, more particularly a surface hardening agent, whichpreferably is chosen from the following series of products: impregnationagents, pore-sealing agents, lacquers, resins, oils, paraffins and thelike.

In FIG. 22, such impregnation 88 is represented schematically. Thistreatment can be performed over the complete surface of the sides 2-3and/or 26-27 or only over specific portions hereof, for exampleexclusively on the surfaces of the tongue 9 and the groove 10.

The treatment with a surface densifying agent offers, in combinationwith the snap-together effect, the advantage that in various aspectsbetter coupling characteristics are obtained. As a result of this, thecoupling parts 4-5 and/or 28-29 better keep their shape and strength,even if the floor panels 1 are engaged and disassembled repeatedly. Inparticular, if the core 8 is made of HDF, MDF or similar materials, bymeans of this treatment a better quality of surface condition isobtained, such that no abrasion of material occurs during engaging, orduring disassembling.

This treatment also offers the advantage that, at least in the case of asurface hardening, the aforementioned elastic tensioning effect isenhanced.

The present invention is in no way limited to the forms of embodimentdescribed by way of example and represented in the figures, however,such floor covering and the pertaining floor panels 1 can be embodied invarious forms and dimensions without departing from the scope of theinvention.

For example, the various characteristics which are described by means ofthe represented embodiments or examples may be selectively combined witheach other.

Furthermore, all embodiments of coupling elements described before canbe applied at the longer side as well as at the shorter side of a panel.

What is claimed is:
 1. A floor covering comprising a hard floor panelhaving a substantially planar underside and at least two opposed sideedges, said side edges including complementary coupling parts configuredto cooperate with identical cooperative complementary coupling parts ofanother one of said panel, said coupling parts comprising substantiallya tongue and a groove extending along panel side edges generallyparallel to the panel underside and including integrated mechanicallocking elements, said tongue, groove and locking elements formed in onepiece with the panel, said tongue, groove and locking elements arrangedto prevent drifting apart of the floor panel when coupled by saidcoupling parts to another one of said floor panel in a directionperpendicular to the adjacent side edges of the coupled panels, andparallel to the underside of the panel; a coupling part of said panel,when engaged with a complementary coupling part of another one of saidpanel, configured and arranged to produce a biasing force between suchcoupled panels tending to urge the panels towards each other; at leastone of said coupling parts including an elastically bendable portionhaving a relaxed unbent position, and which, when in a coupledcondition, is at least partially bent out of its normal relaxed positionand thereby provides said biasing force; wherein the elasticallybendable portion of said one of said coupling part comprises a lower lipdefined at least in part by a lower side of the groove of said couplingparts, said lower lip cooperating with a mating portion of a tongue of acooperating coupling part; wherein said lip when bent extends in adownward direction relative to the panel underside when the panel iscoupled by cooperative complementary coupling parts to another one ofsaid panel; wherein the panel comprises a core comprising a materialselected from the group consisting of HDF and MDF board; said lower lipis substantially formed of said core; one of said locking elementscomprises a recess in said lower lip, said recess having a lowermostbottom area; said groove having a deepest point within the panel; andwherein said elastically bendable portion of the lower lip comprises aportion of said lower lip located between the deepest point of saidgroove and the lowermost bottom area of said recess; wherein thebendable portion of the lower lip includes a side wall of said recessthat slopes downwardly in a direction extending from a distally outerarea of said lip towards a proximally inner area of said lip.
 2. A floorcovering comprising a hard floor panel having a substantially planarunderside and at least two opposed side edges, said side edges includingcomplementary coupling parts configured to cooperate with identicalcooperative complementary coupling parts of another one of said panel,said coupling parts comprising substantially a tongue and a grooveextending along panel side edges generally parallel to the panelunderside and including integrated mechanical locking elements, saidtongue, groove and locking elements formed in one piece with the panel,said tongue, groove and locking elements arranged to prevent driftingapart of the floor panel when coupled by said coupling parts to anotherone of said floor panel in a direction perpendicular to the adjacentside edges of the coupled panels, and parallel to the underside of thepanel; a coupling part of said panel, when engaged with a complementarycoupling part of another one of said panel, configured and arranged toproduce a biasing force between such coupled panels tending to urge thepanels towards each other; at least one of said coupling parts includingan elastically bendable portion having a relaxed unbent position, andwhich, when in a coupled condition, is at least partially bent out ofits normal relaxed position and thereby provides said biasing force;wherein said floor panel is rectangular and includes two pairs ofopposed side edges; said coupling parts and locking elements areprovided on all side edges of the panel; and wherein said lockingelements are provided on at least two side edges that are perpendicularto and meet each other whereby, when the panel is coupled withcomplementary coupling parts of identical ones of said panel at allopposed edges, the panels are locked together by said locking elementsat all coupled side edges; wherein said coupling parts are configuredand arranged to enable coupling of complementary coupling parts ofidentical ones of said panel to each other by rotation of one panelrelative to the other, said coupling parts configured such that uponrotation of one panel relative to the other panel the elasticallybendable portion of one coupling part is bent; and wherein at coupledside edges of the coupled panels the coupling parts are configured suchthat one panel is movable relative to the other by shifting the onerelative to the other in a direction parallel to the coupled side edges;said shifting of one panel relative to the other maintaining the bentcondition of the elastically bendable portion of the lower lip while thepanels are coupled.
 3. A method of assembling a floor coveringcomprising cooperating rectangular hard floor panels each having asubstantially planar underside and at least two opposed side edgesincluding complementary coupling parts arranged to cooperate withidentical complementary coupling parts of another one of said panels,said complementary coupling parts substantially comprising a tongue anda groove extending generally parallel to said underside, said couplingparts further including integrated mechanical locking elements whichprevent the drifting apart of coupled ones of said panels away from eachother in directions perpendicular to the respective coupled side edgesand parallel to the undersides of the panels, said coupling partsdefining at least in part a lower lip which defines at least a portionof a lower side of each groove of the coupling parts and an upper liplocated above each groove area adjacent the upper surface of the panel;said lower lip extending distally beyond the upper lip; said lockingelements including a portion of said lower lip which slopes downwardlyin a direction extending from a distally outer location towards aproximally inner location, said portion located at least in part on apart of the lower lip extending beyond said upper lip, a lower side ofsaid tongue that is inclined downwardly in a direction extending fromproximal inner location of said tongue to a distally outer locationthereof; said portion of said lower lip that slopes downwardlycooperating with said lower side of the tongue that is inclined, saidlower lip including an elastically bendable portion that must beelastically bent downwardly to enable coupling of a complementary pairof tongue and groove coupling parts; comprising the steps of: laying afirst one of said panels on a support surface; coupling a second one ofsaid panels to said first one panel along first and second complementaryside edges of the panels by fitting a tongue of one panel into acomplementary groove of the other panel until said downwardly slopingportion of said lower lip engages said downwardly inclined lower side ofsaid tongue while bending the lower lip elastically in a downwarddirection; and maintaining said lower lip in a bent condition after suchcoupling to effectively bias the sloped and inclined portions of thelower lip and tongue together and to produce a resultant biasing forcemaintaining the panels compressed against each other at the coupled sideedges.
 4. A method according to claim 3, wherein said second panel iscoupled to the first panel by first fitting the tongue and groove intoeach other with the second panel angled upwardly with respect to thefirst panel and then subsequently angling down the second panel to bringthe two panels into a coplanar relationship, and causing by said anglingdown that the bendable portion of the lower lip of the first panel isresiliently bent downwardly over a small distance.
 5. The methodaccording to claim 3, wherein the second panel is coupled to the firstpanel by first fitting the tongue and groove into each other, saidfitting being carried out by shifting the second panel relative to thefirst panel with both panels in a substantially coplanar relationship,and causing by said shifting that the bendable portion of the lower lipof the first panel is deflected downwardly over a small distance.
 6. Themethod according to claim 3, wherein said tongue, groove, lips andlocking elements are provided on coupling parts located at opposed pairsof opposite side edges, said method comprising the additional step of:coupling a third one of said panels to the first and second ones of saidpanels respectively along complementary third and fourth side edges ofthe panels that extend perpendicular to each other; and causing by saidcoupling that an elastically bendable portion of a lower lip of the lastrecited side edges is elastically deflected in a downward direction, thereturn force of the deflected portion of the lip providing the resultantbiasing force maintaining the panels compressed against each other alongsaid third and fourth side edges.
 7. The method according to claim 6,wherein the coupling of the panels is created by the steps of: couplingthe third panel to the first panel by first fitting a tongue of thethird panel into a complementary groove of the first panel with thethird panel angled upwardly with respect to the first panel, thenangling down the third panel so that the first and third panels arecoplanar, and causing by said angling down that the bendable portion ofthe lower lip of the first panel is deflected downwardly over a smalldistance to provide a resilient biasing force urging said first andthird panels together; coupling the third panel to the second panel byfirst partially fitting a tongue of the third panel into a complementarygroove of the second panel and then shifting the third panel toward thesecond panel with the second and third panels in a coplanar relationshipto fully couple the respective tongue and groove of the third and secondpanels; said third and second panels being thereby located in a coplanarcondition with the bendable portion of the lower lip of the second panelremaining in a downwardly deflected condition to provide a resilientbiasing force urging the third and second panels together.
 8. The methodaccording to claim 6, wherein the coupling of the panels is created bythe steps of: coupling the third panel to the first panel by first fullycoupling together a tongue and groove of the third and first panels byshifting the third panel relative to first panel with both panels in acoplanar relationship, said shifting causing a bendable portion of thelower lip of the first panel to become and remain deflected downwardlyover a small distance while the panels are coupled; and coupling thethird panel to the second panel by coupling the tongue and groove of therespective third and second panels, said coupling being carried out byshifting the third panel relative to the second panel with the panels ina substantially coplanar relationship; causing the bendable portion ofthe lower lip of the second panel to become and remain deflecteddownwardly over a small distance while the third and second panels arecoupled.
 9. The method according to claim 3, including the step oflaying all the panels over a flexible underlay, said flexible underlayaccommodating the downwardly bent portions of the panel lips with theupper surfaces of the panels lying in a common plane.
 10. A floorcovering comprising a laminated hard floor panel having a wood-basedcore material selected from the group consisting of High DensityFibreboard (HDF) and Medium Density Fibreboard (MDF), said panelcomprising a first pair and a second pair of opposed side edges, saidpanel further comprising generally complementary coupling parts locatedat both of the pairs of said side edges, said coupling parts comprisinga tongue and a groove, said tongue and groove when coupled alongadjacent side edges of two ones of said panel comprising integralmechanical locking elements, said coupling parts as well as saidmechanical locking elements being integral and made in one piece withsaid core material, said coupling parts together with said lockingelements arranged so as to enable a locking in a direction perpendicularto the plane of the floor covering as well as in a directionperpendicular to the coupled side edges and parallel to a planeincluding the panels that are coupled, wherein said coupling parts andthe mechanical locking elements of at least said second pair of oppositeside edges are configured such that two identical ones of said floorpanel are coupled by shifting them laterally towards each other in asubstantial planar fashion, and wherein the locking elements of saidsecond pair of opposite side edges provide a snap-together couplingproviding a snap-action during the coupling of two panels by shiftingthem laterally towards each other, said snap action being deliveredsubstantially by said core material; wherein said locking elementscomprise a recess located in a lower lip extending at least to a sideedge and defining at least in part a lower side of said groove; and aprotrusion provided at a lower side of said tongue; wherein the-panelsat the side edge comprising the groove, of at least one of the side edgeof both pairs of the side edges, include an upper lip above the groove,said upper lip defining at least in part an upper side of said groove,and said upper lip terminating at a distal outer end, wherein said lowerlip extends distally beyond the distal outer end of the upper lip, andfurther wherein the recess is located in the lower lip in an area of thelower lip that is located at least partly beyond the distal outer end ofthe upper lip.
 11. The floor covering according to claim 10, wherein theconfiguration of the tongue and the lower lip are such that a tongue ofsaid panel becomes automatically lodged in the groove of anotheridentical one of said panels by laterally moving the panels towards eachother in approximately a plane including the panels during which thetongue is partially inserted into the groove before the lower lip isdeformed.
 12. The floor covering according to claim 11, wherein saidpanel becomes automatically lodged in the groove of another identicalone of said panels by laterally moving the panels towards each other inapproximately a plane including the panels starting from positions atwhich the panels are completely separated from each other.
 13. The floorcovering according to claim 10, wherein the first pair of side edges aswell as the second pair of the side edges comprise coupling parts andlocking elements including a lower lip extending beyond the upper lip.14. The floor covering according to claim 10, wherein one pair of theside edges comprises coupling parts in the form of a tongue and a grooveand wherein the locking elements of this pair of side edges are locatedcompletely inside the groove.
 15. The floor covering according to claim14, wherein the groove is formed by upper and lower lips, the upper lipand the lower lip bordering the groove are of equal length.
 16. Thefloor covering according to claim 15, wherein said floor panels areelongated and the side edges having the upper lip and the lower lip ofequal length is located at one of the short sides of the panels.
 17. Thefloor covering according to claim 10, wherein the lower lip extendsbeyond the upper lip over a distance which is smaller than the thicknessof the panel.
 18. The floor covering according to claim 10, wherein atat least one pair of the edges, the locking elements comprise inclinedcontact surfaces.
 19. The floor covering according to claim 18, whereinthe contact surfaces define a tangent line which in respect to the planeof the floor covering shows an inclination which is comprised between30° and 70°.
 20. The floor covering according to claim 11, wherein thelocking elements comprise at least one contact surface which isperpendicular to the plane of the panels.
 21. The floor coveringaccording to claim 14, wherein one pair of the side edges comprisescoupling parts in the form of a tongue and a groove and wherein thelocking elements of this pair of side edges are located completelyinside the groove; and wherein the locking elements comprise at leastone contact surface which is perpendicular to the plane of the panels.22. The floor covering according to claim 10, wherein said lower lipcomprises an increasing thickness from the recess towards the innermostpoint of said groove.
 23. A floor covering comprising a laminated hardfloor panel having a wood-based core material selected from the groupconsisting of High Density Fibreboard (HDF) and Medium DensityFibreboard (MDF), said panel comprising a first pair and a second pairof opposed side edges, said panel further comprising generallycomplementary coupling parts located at both of the pairs of said sideedges, said coupling parts comprising a tongue and a groove, said tongueand groove when coupled along adjacent side edges of two ones of saidpanel comprising integral mechanical locking elements, said couplingparts as well as said mechanical locking elements being integral andmade in one piece with said core material, said coupling parts togetherwith said locking elements arranged so as to enable a locking in adirection perpendicular to the plane of the floor covering as well as ina direction perpendicular to the coupled side edges and parallel to aplane including the panels that are coupled, wherein said coupling partsand the mechanical locking elements of at least said second pair ofopposite side edges are configured such that two identical ones of saidfloor panel are coupled by shifting them laterally towards each other ina substantial planar fashion, and wherein the locking elements of saidsecond pair of opposite side edges provide a snap-together couplingproviding a snap-action during the coupling of two panels by shiftingthem laterally towards each other, said snap action being deliveredsubstantially by said core material; at least one of said pairs of edgescomprising a lower lip defining at least in part a bottom side of agroove of said coupling parts and extending distally beyond a respectivegroove opening, and wherein said locking elements comprise a protrusionextending from the lower side of a tongue of said pairs of edges and acooperating recess in said lower lip, said protrusion and recess fittingtogether when ones of said panel are coupled by said tongue and groove;wherein, when a complementary tongue and groove are coupled, saidprotrusion and recess meet each other at contiguous contact surfaces ata common plane of tangency that with respect to a common plane of thecoupled panels is inclined inwardly from a distally outer area towards adistally inner area at an angle less than 90°.
 24. The floor panelaccording to claim 23, wherein the angle is between 30-70°.
 25. A floorcovering comprising a laminated hard floor panel having a wood-basedcore material selected from the group consisting of High DensityFibreboard (HDF) and Medium Density Fibreboard (MDF), said panelcomprising a first pair and a second pair of opposed side edges, saidpanel further comprising generally complementary coupling parts locatedat both of the pairs of said side edges, said coupling parts comprisinga tongue and a groove, said tongue and groove when coupled alongadjacent side edges of two ones of said panel comprising integralmechanical locking elements, said coupling parts as well as saidmechanical locking elements being integral and made in one piece withsaid core material, said coupling parts together with said lockingelements arranged so as to enable a locking in a direction perpendicularto the plane of the floor covering as well as in a directionperpendicular to the coupled side edges and parallel to a planeincluding the panels that are coupled, wherein said coupling parts andthe mechanical locking elements of at least said second pair of oppositeside edges are configured such that two identical ones of said floorpanel are coupled by shifting them laterally towards each other in asubstantial planar fashion, and wherein the locking elements of saidsecond pair of opposite side edges provide a snap-together couplingproviding a snap-action during the coupling of two panels by shiftingthem laterally towards each other, said snap action being deliveredsubstantially by said core material; at least one of said pairs of edgescomprising a lower lip defining at least in part a bottom side of agroove of said coupling parts and extending distally beyond a respectivegroove opening, and wherein said locking elements comprise a protrusionextending from the lower side of a tongue of said pairs of edges and acooperating recess in said lower lip, said protrusion and recess fittingtogether when ones of said panel are coupled by said tongue and groove;said panel including an upper outer edge and wherein the protrusion andrecess include engageable complementary contact surfaces located onradii (R1-R2) centered within a circle which extends within a radius of3 mm around the upper outer edge of the panel.
 26. A method ofassembling a floor covering comprising hard floor panels of rectangularshape, said panels each including complementary coupling parts atopposed side edges of the panels, said coupling parts arranged tocooperate with complementary coupling parts of another one of saidpanel, said coupling parts comprising substantially a tongue, a groove,and integrated locking elements collectively arranged to prevent thedrifting apart of two coupled ones of said floor panel in a directionparallel to the edges along which the panels are coupled and parallel toa plane including the floor panels, said panels each including distallyextending upper and lower lips on opposite sides of said groove, saidlower lip including an elastically flexible portion and defining atleast in part a lower side of the groove and extending distally beyondthe upper lip, and wherein one of said locking elements comprises atleast in part a portion of the elastically flexible portion of the lowerlip that extends beyond the upper lip and which is inclined downwardlyin a direction extending inwardly from the distal end area of said lip,said locking element cooperating with a surface of the lower side of thetongue which slopes downwardly in a direction extending outwardly from aproximal area of the tongue toward a distal area thereof, said methodcomprising the steps of: laying a first one of said hard floor panel ona support surface; placing a second one of said panel next to a sideedge of the first one of said panel, such that a tongue of one of saidpanel side edges lies next to a groove of the other one of said panelside edges; shifting the panels towards each other to move a tongue intoa groove and to bend a flexible portion of a lower lip downwardly, saidshifting causing the inclined and sloped surfaces of the tongue andgroove respectively to engage each other in coupled relationship withthe panels biased towards each other by the returning force of thedownwardly bent lower lip; wherein a third panel is coupled to apreviously laid one or more of said first and second ones of said panelby placing the tongue of the third panel in a complementary groove ofone or more of the previously laid panels, and wherein the second one ofsaid panel, before being coupled with the first one of said panel, iscoupled to an already previously laid one or more of said panel usingthe steps of: directing a tongue of the third one of said panel towardsa groove of an already laid panel or panels and inserting a tongue ofthe third one of said panel at least partially into the groove of analready laid panel or panels while the third one panel is angledupwardly relative to the already laid panel or panels; angling down thethird one of said panel so that the inclined locking elements arebrought adjacent each other; after such angling down of the third one ofsaid panel, laterally moving the third one of said panel towards thepreviously laid one or more panels with the panels in a common plane tocompletely engage the tongue, groove and locking elements of the thirdone of said panel with a complementary tongue, groove and lockingelement of the previously laid panel or panels.
 27. A floor coveringcomprising a laminated hard floor panel having a wood-based corematerial selected from the group consisting of High Density Fibreboard(HDF) and Medium Density Fibreboard (MDF), said panel comprising a firstpair and a second pair of opposed side edges, said panel furthercomprising generally complementary coupling parts located at both of thepairs of said side edges, said coupling parts comprising a tongue and agroove, said tongue and groove when coupled along adjacent side edges oftwo ones of said panel comprising integral mechanical locking elements,said coupling parts as well as said mechanical locking elements beingintegral and made in one piece with said core material, said couplingparts together with said locking elements arranged so as to enable alocking in a direction perpendicular to the plane of the floor coveringas well as in a direction perpendicular to the coupled side edges andparallel to a plane including the panels that are coupled, wherein saidcoupling parts and the mechanical locking elements of at least saidsecond pair of opposite side edges are configured such that twoidentical ones of said floor panel are coupled by shifting themlaterally towards each other in a substantial planar fashion, andwherein the locking elements of said second pair of opposite side edgesprovide a snap-together coupling providing a snap-action during thecoupling of two panels by shifting them laterally towards each other,said snap action being delivered substantially by said core material;wherein said coupling parts and locking elements of the first pair ofside edges are configured and dimensioned so as to enable two identicalones of said floor panel to be coupled at the side edges at least byturning one of said floor panels relative to the other.
 28. The floorcovering according to claim 27, wherein said coupling parts and lockingelements of the first pair of side edges are configured and dimensionedso as to enable identical ones of said floor panel to be laterallycoupled at these side edges exclusively by turning one of said floorpanels relative to the other.
 29. The floor covering according to claim27, wherein said floor panels are elongated and the first pair ofopposed side edges is formed by the longer side edges, whereas thesecond pair of opposed side edges is formed by the shorter side edges.30. The floor covering according to claim 27, wherein said couplingparts and said locking elements of both of the pairs of side edges areconfigured and dimensioned so as to enable identical ones of said floorpanel to be laterally engaged, as well as disengaged, at their sideedges by turning one of said floor panel relative to the other.